Communication networks are generally based on either a packet-switching protocol, a circuit-switching protocol, or some combination of the two, such as, for example, an asynchronous transfer mode (ATM) protocol. In a packet-switching protocol, messages are divided into packets before they are sent. Each packet is then individually transmitted and can even follow different routes to its destination based on routing information contained in the packet. Once all the packets forming a given message arrive at the target destination, they are recompiled into the original message. In a circuit-switching protocol, on the other hand, the message path is determined prior to sending the data. A dedicated channel is allocated for transmission between a source and a destination. Because routing is predetermined, transmitted messages need not include routing information, as in the case of packet switching. Circuit switching is ideally suited for applications in which data must be transmitted quickly and must arrive in the same order in which it was sent. For this reason, most real-time data applications, such as, for example, live audio and/or video streaming, employ a circuit-switching protocol.
Time Division Multiplexing (TDM), which is a well-known circuit-switching protocol, allocates multiple data streams to respective time slots and repeatedly transmits a fixed sequence of time slots over a single transmission channel. TDM is predominantly used in telecommunications networks. Synchronous network protocols, such as, for example, Synchronous Optical Network (SONET) and Synchronous Data Hierarchy (SDH) use TDM to transport voice and data through the core of the network. A more detailed description of these and other conventional protocols may be found, for example, in the articles D. Bertsekas et al., “Data networks, Second Edition,” Prentice Hall (1992), J. Goralski, “SONET, Second Edition,” McGraw-Hill, USA (2000), R. Perlman, “Interconnections: Bridges, Routers, Switches and Internetworking Protocols,” Addison-Wesley (1997), M. Sexton, “Broadband Networking: ATM, SCH, and SONET,” Artech House, Mass. (1997), S. Kershav, “An Engineering Approach to Computer Networks,” Addison-Wesley (1997), A. Tannenbaum, “Computer Networks,” Prentice Hall (1996), D. Corner, “Internetworking with TCP/IP,” NJ: Prentice Hall (2000), all of which are incorporated herein by reference.
One class of switches known as non-blocking cross-connect switches are typically employed in a synchronous TDM network. A connection between an input and an output of a switch is considered to be blocked if there is no signal path available through the switch. Signal paths must be simultaneously established for all connections in the synchronous TDM network, a condition which is a requirement for admission of a new connection. A non-blocking cross-connect switch must guarantee transmission of data through the switch at a specified aggregate transmission rate. Some conventional approaches to designing non-blocking cross connects include time-division switching, space-division switching, and multistage switching which is essentially a combination of time-division and space-division switching.
Each of the above techniques for routing data through a network, however, incorporate certain undesirable characteristics. Accordingly, there exists a need for a cross-connect architecture for use in a circuit-switching network that overcomes the disadvantages of conventional methodologies.